For the last 24 years, I have lived my life by the sounds of plastic injection machines. I have often seen engineers sitting with their laptops, unable to catch the ‘disease’ brewing inside the machine. Today, I want to talk about a problem that stays hidden from the eyes but ruins your production: The Invisible Wear of the Screw and Barrel. Where does the problem hide?

A screw and barrel do not wear out overnight. It is like the slow aging of human bones. As they grind over time, the gap or ‘clearance’ between them increases. When this happens, the molten plastic starts leaking backward instead of moving forward. We call this ‘backflow’ in technical terms. As a result, no matter how much injection pressure you set on the machine, the right pressure never reaches the mold.

How do you know your machine is 'aging'?

You can sense these signs even before opening the machine:

You notice the weight of the finished products varies every time (Shot weight variation).

During injection, the cushioning position is not steady; it fluctuates or drops.

A product that used to take 20 seconds to produce now takes 22-23 seconds.

My 24 Years of Practical Solution

I always say, prevention is better than cure.

If you work with glass-fiber-reinforced plastics, you must use hardened screws. Processing these with regular screws will cause rapid wear.

Never do a ‘Cold Start’ on a winter morning or after a long break. This puts extreme pressure on the screw and can damage it.

At least once a year, the screw and barrel should be precisely measured using a micrometer.

Remember, my formal education may be limited, but the machine never lies to me. If you understand the language of the machine, your production will never stop. Catching these small, invisible problems in time can save your factory from huge financial losses.